Hydrocarbons characterized by their uniform carbon ring structure and their often pleasant aroma. Commercial petroleum aromatics are benzene, toluene, and xylene. These three are often referred to by the acronym BTX. These chemicals are used as high octane components in gasoline. Aromatics have been judged to be undesirable in some finished motor fuels with various state and federal regulations geared toward reducing their levels. CARB diesel fuel in the state of California mandates a low aromatics composition. As Billed Rates – A policy requiring pipelines to flow through gas costs to their customers in the same manner as they are billed to the pipeline.